At least 600 people in Israel have been killed in the surprise attacks by Hamas and at least 370 have been killed in retaliatory strikes in Gaza, Israeli and Palestinian health officials said Sunday.

At least 2,156 people have been injured in Israel, according to the Israeli Health Ministry. At least, 2,200 have been injured in Gaza, the Palestinian Health Authority said.

-ABC News' Joseph Simonetti

Republican presidential candidate Chris Christie slammed the dysfunctionin> the U.S. House of Representatives, where a small group of Republican lawmakers last week voted along with the Democratic minority to oust Speaker Kevin McCarthy, for leaving it without a way to pass legislation, including foreign aid to Israel.

"What I would be doing is making sure, one, that Israel has everything that it needs to be able to take whatever actions it needs to take. And this is the problem with not having a speaker right now," Christie, the former New Jersey governor, told ABC News' "This Week" anchor George Stephanopoulos.

Christie, a former ABC News contributor, added, "The actions taken by some members of my party were wholly irresponsible without this going on. They're now even putting a brighter light on the irresponsibility of not having someone in place."

Christie also said his top priorities if he were president would be engaging allies in the region, such as Jordan and Saudi Arabia, to keep the conflict from spreading and to serve as a "sounding board" to Israeli Prime Minister Benjamin Netanyahu to help him "think through the ramifications of every step they're going to take to defend themselves and to try to do the best they can to eliminate the leadership of Hamas."

-ABC Nicholas Kerr

For the first time since Saturday's surprise attack by Hamas militants, the Israeli government confirmed that a number of people, including civilians, have been taken hostage.

Israel's Government Press Office said Sunday that at least 100 Israeli citizens and soldiers are being held hostage by Hamas fighters.

U.S. Secretary of State Antony Blinken said in separate interviews on CNN and NBC News that there is a possibility Americans are among those killed or taken hostage and that the U.S. Department of State is investigating.

-ABC News' Joe Simonetti

Secretary of State Antony Blinken on Sunday pushed back on growing Republican criticism that the White House's decision to allow the transfer of some $6 billion of Iran's oil revenue, in exchange for the release of five American detainees, was a sign of "appeasement" ahead of the surprise attack on Israel by Hamas militants.

"Not a single dollar from that account has been spent to date and, in any event, is very closely and carefully regulated by the Treasury Department," Blinken told ABC's "This Week" anchor George Stephanopoulos.

Blinken stressed that the funds are designated solely for humanitarian purposes and are not U.S. tax dollars.

-ABC News' Adam Carlson

National Security Council spokesperson John Kirby avoided saying if the U.S. believed Israel's calls for civilians in Gaza to evacuate in the next 24 hours was possible but acknowledge that it was a "tall order" given how densely populated the area is.

"Well, I think we're going to be careful not to get into armchair quarterbacking the tactics on the ground by the IDF. What I can tell you is we understand what they're trying to do. They're trying to move civilians out of harm's way and giving them fair warning. Now, it's a tall order. It's a million people, and it's a very urban, dense environment, already a combat zone. I don't think anybody's underestimating the challenge here of affecting that evacuation," Kirby said in an interview on CNN Friday morning.

"But it's pretty clear that what they're trying to do is to the maximum extent possible avoid civilian casualties and also separate Hamas from the human shields. I mean, Hamas actually gave a counterorder telling Palestinians in Gaza to stay at home. Why? Because having human shields, they think, protects them," Kirby continued.

Asked about their efforts to secure a safe passage for civilians out of Gaza, Kirby reiterated that the U.S. is talking to Israel and Egypt but would not comment further on progress.

On the Rafah crossing specifically, Kirby said "So far it's still closed. But that doesn't mean were not going to still try as hard as we can to talk to the Israelis and Egyptians about getting it open and having some sort of safe passage out. It's important that we also continue to work to make sure that humanitarian assistance can get in. The United States has no intention of stopping our efforts to continue to deliver humanitarian assistance, but there has to be a path in, there has to be a path out."

Kirby had no update on the Americans who are believed to be held hostage in Gaza and could not confirm reports that 13 hostages have been killed by Israeli airstrikes, as Hamas has claimed.

-ABC News' Molly Nagle